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tcp: fix cookie_init_timestamp() overflows

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cookie_init_timestamp() is supposed to return a 64bit timestamp
suitable for both TSval determination and setting of skb->tstamp.

Unfortunately it uses 32bit fields and overflows after
2^32 * 10^6 nsec (~49 days) of uptime.

Generated TSval are still correct, but skb->tstamp might be set
far away in the past, potentially confusing other layers.

tcp_ns_to_ts() is changed to return a full 64bit value,
ts and ts_now variables are changed to u64 type,
and TSMASK is removed in favor of shifts operations.

While we are at it, change this sequence:
		ts >>= TSBITS;
		ts--;
		ts <<= TSBITS;
		ts |= options;
to:
		ts -= (1UL << TSBITS);

Fixes: 9a568de481 ("tcp: switch TCP TS option (RFC 7323) to 1ms clock")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2023-10-20 12:57:37 +00:00 committed by David S. Miller
parent 225d9ddbac
commit 73ed8e0338
2 changed files with 8 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
include/net/tcp.h
View File

@ -805,7 +805,7 @@ static inline u32 tcp_time_stamp(const struct tcp_sock *tp)
}
/* Convert a nsec timestamp into TCP TSval timestamp (ms based currently) */
static inline u32 tcp_ns_to_ts(u64 ns)
static inline u64 tcp_ns_to_ts(u64 ns)
{
return div_u64(ns, NSEC_PER_SEC / TCP_TS_HZ);
}

20
net/ipv4/syncookies.c
View File

@ -41,7 +41,6 @@ static siphash_aligned_key_t syncookie_secret[2];
* requested/supported by the syn/synack exchange.
*/
#define TSBITS 6
#define TSMASK (((__u32)1 << TSBITS) - 1)
static u32 cookie_hash(__be32 saddr, __be32 daddr, __be16 sport, __be16 dport,
u32 count, int c)
@ -62,27 +61,22 @@ static u32 cookie_hash(__be32 saddr, __be32 daddr, __be16 sport, __be16 dport,
*/
u64 cookie_init_timestamp(struct request_sock *req, u64 now)
{
struct inet_request_sock *ireq;
u32 ts, ts_now = tcp_ns_to_ts(now);
const struct inet_request_sock *ireq = inet_rsk(req);
u64 ts, ts_now = tcp_ns_to_ts(now);
u32 options = 0;
ireq = inet_rsk(req);
options = ireq->wscale_ok ? ireq->snd_wscale : TS_OPT_WSCALE_MASK;
if (ireq->sack_ok)
options |= TS_OPT_SACK;
if (ireq->ecn_ok)
options |= TS_OPT_ECN;
ts = ts_now & ~TSMASK;
ts = (ts_now >> TSBITS) << TSBITS;
ts |= options;
if (ts > ts_now) {
ts >>= TSBITS;
ts--;
ts <<= TSBITS;
ts |= options;
}
return (u64)ts * (NSEC_PER_SEC / TCP_TS_HZ);
if (ts > ts_now)
ts -= (1UL << TSBITS);
return ts * (NSEC_PER_SEC / TCP_TS_HZ);
}